High frequency magnetic thin film, composite magnetic thin film and magnetic device using them

ABSTRACT

A high frequency magnetic thin film characterized by comprising a first layer made of a T-L composition (here, T is Fe or FeCo, and L is one or more of C, B, and N) and a second layer comprising a Co-based amorphous alloy arranged on either of the surfaces of the first layer. The high frequency magnetic thin film is a multilayer film of a plurality of the first layers and a plurality of the second layers or desirably is a multilayer film of alternately laminated first and second layers. The high frequency magnetic thin film of the present invention exhibits the properties such that the real part (μ′) of the complex permeability is 400 or more at 1 GHz, a quality factor Q (Q=μ′/μ″) is 4 or more, and a saturation magnetization is 14 kG (1.4 T) or more.

CROSS-REFERENCE TO THE RELATED APPLICATIONS

This is a continuation of application Ser. No. 10/502,490 filed Jan. 11,2005 now U.S. Pat. No. 7,224,254, which is a national phase ofinternational application No. PCT/JP03/00163 filed Jan. 10, 2003, theentire contents of which are incorporated by reference. This applicationalso claims benefit of priority under 35 U.S.C. § 119 to Japanese PatentApplication No. 2002-007059 filed Jan. 16, 2002, Japanese PatentApplication No. 2002-117079 filed Apr. 19, 2002 and Japanese PatentApplication No. 2002-366192 filed Dec. 18, 2002, the entire contents ofall of which are incorporated by reference.

TECHNICAL FIELD

The present invention relates to a magnetic thin film which has highsaturation magnetization, and exhibits high permeability and a highquality factor Q in the high frequency band of GHz range, in particular,high frequency planar magnetic devices such as a thin film inductor, athin film transformer, or a magnetic thin film inductor used in amonolithic microwave integrated circuit (MMIC).

BACKGROUND ART

Miniaturization and sophistication of magnetic devices are followed bydemand for magnetic thin film materials having high saturationmagnetization and high permeability in the high frequency of GHz range.

For example, the monolithic microwave integrated circuit (MMIC), forwhich demand is growing mainly for use in wirelesstransmitters/receivers and portable information devices, is a highfrequency integrated circuit having a configuration in which activeelements such as transistors and passive elements such as transmissionline, resistors, capacitors and inductors are integrated on asemiconductor substrate made of Si, GaAs, InP and the like.

In such an MMIC, the passive elements, in particular, the inductors andcapacitors occupy larger areas than the active elements. The occupationof larger areas by the passive elements as a result leads to massconsumption of expensive semiconductor substrates, namely, the cost riseof the MMIC. Accordingly, now it is a challenge to reduce the areasoccupied by the passive elements for the purpose of reducing the chiparea and thereby lowering the manufacturing cost of the MMIC.

As the inductors used in MMICs, planar spiral coils are frequently used.In this connection, there has already been proposed a method (in otherwords, a method for obtaining an inductance comparable with aconventional inductance even by using a small occupied area) forincreasing the inductance of such a spiral coil by inserting a softmagnetic thin film on the top and back sides or on one side of thespiral coil (for example, J. Appl. Phys., 85, 7919 (1999)).

However, for the purpose of applying a magnetic material to the inductorin an MMIC, it is demanded that firstly, a thin film magnetic material,which is high in permeability and low in loss in the high frequency ofGHz range, should be developed. Additionally, high resistivity is alsodemanded for the purpose of reducing the eddy current loss.

So far, alloys comprising as the main component Fe or FeCo have beenwell known as materials having high saturation magnetization. However,when a magnetic thin film made of an Fe-based alloy or an FeCo-basedalloy is prepared by means of a deposition technique such as thesputtering technique, the saturation magnetization of the film obtainedis high, but the coercivity thereof is high and the resistivity thereofis low, so that satisfactory high frequency properties thereof can behardly obtained.

On the other hand, Co-based amorphous alloys are known as materialsexcellent in soft magnetic properties. Such a Co-based amorphous alloymainly comprises an amorphous substance comprising Co as the maincomponent and one or more elements selected from the group consisting ofY, Ti, Zr, Hf, Nb, Ta and the like. However, when a Co-based amorphousalloy having zero magnetostriction composition is formed by means of adeposition technique such as the sputtering technique, the permeabilityof the film obtained is high, but the saturation magnetization thereofis of the order of 11 kG (1.1 T), and lower than those of Fe-basedalloys. Additionally, for the frequencies higher than 100 MHz, the losscomponent (the imaginary part of the permeability, μ″) becomes large andthe quality factor Q comes to be 1 or less, so that the film concernedcannot be judged to be suitable as a magnetic material to be used in thehigh frequency of GHz region.

For the purpose of actualizing the inductor for use in the GHz region byuse of such hardly applicable materials, an attempt has been made toshift the resonance frequency to the higher frequencies bymicro-patterning a magnetic thin film so as to be increased in shapemagnetic anisotropy energy (for example, J. Magnetics Soc. Japan, 24,879 (2000)). However, this method involves a problem such that theproduction process tends to be complicated and additionally theeffective permeability of the magnetic thin film is lowered.

Under such actual circumstances as described above, various proposalshave hitherto been made for the purpose of improving the high frequencyproperties of the soft magnetic thin film. The fundamental guidelinesfor the improvement include the suppression of the eddy current loss andthe increase of the resonance frequency. Specific measures forsuppressing the eddy current loss which have been proposed include amultilayered configuration formation by alternately laminating amagnetic layer and an insulating layer (a high electric resistancelayer) (for example, Japanese Patent Laid-Open No. 7-249516) and agranularization of metals and nonmetals (oxides, fluorides) (forexample, J. Appl. Phys., 79, 5130 (1996)). However, the multilayer filmmethods involve the insertion of the high electric resistancenonmagnetic phase and hence lead to a problem such that the saturationmagnetization is lowered. In the case of the metal-nonmetal granularfilm, a permeability is 200 or less, leading to a problem that thepermeability is low.

On the other hand, high saturation magnetization thin films each made ofa multilayer film formed by alternately laminating a soft magnetic layerand a high saturation magnetization layer has been investigated. Morespecifically, there have been reported various combinations such asCoZr/Fe (J. Magnetics Soc. Japan, 16, 285 (1992)), FeBN/FeN (JapanesePatent Laid-Open No. 5-101930), FeCrB/Fe (J. Appl. Phys., 67, 5131(1990)), and Fe—Hf—C/Fe (J. Magnetics Soc. Japan, 15, 403 (1991)). Anyone of these combinations has an effect of enhancing the saturationmagnetization. However, any one of these combinations cannot yield highpermeability in the high frequency region, no application to the GHzfrequency region being able to be expected.

Under such actual circumstances as described above, the presentinvention has been invented and takes as its object the provision of ahigh frequency magnetic thin film having high permeability and highsaturation magnetization in the high frequency of GHz region.Additionally, the present invention takes as its another object theprovision of a magnetic device using such a magnetic thin film.

DISCLOSURE OF THE INVENTION

The high frequency magnetic thin film of the present invention can beused in the frequency region of several 100 MHz or more, in particular,1 GHz or more. The permeability in such a high frequency region(hereinafter, simply referred to as “high frequency permeability”) is aphysical property related to various physical properties of the sampleconcerned in a complicated manner. Among such physical properties arethe anisotropy field and the saturation magnetization which are mostintimately related to the permeability. Approximately, the product ofthe permeability and the resonance frequency has a relation such thatthe product is proportional to the ½-th power of the anisotropy fieldand the 3/2-th power of the saturation magnetization.

The resonance frequency is represented by the following relation (1):f _(x)=(γ/2π)[H _(k)4πM _(s)]^(1/2)  (1)where f_(r) represents the resonance frequency, γ represents thegyromagnetic constant, H_(k) represents the anisotropy field and 4πM_(s)represents the saturation magnetization.

As the above mentioned, the resonance frequency can be increased byincreasing the anisotropy magnetic field and the saturationmagnetization of the material and thereby the usable limit frequency canbe increased. Now, a calculation is made on the basis of the aboveformula (1) on the anisotropy magnetic field required for increasing upto 2 GHz the resonance frequency of the CoZrNb amorphous alloy thinfilm, which is a typical example of conventional Co-based amorphousalloy thin films. Consequently, the calculation reveals that theanisotropy magnetic field of 44 Oe (3501.52 A/m) or more is required. Ascan be seen from this calculated result, the film concerned whichusually has an anisotropy magnetic field of the order of 15 Oe (1193.7A/m) is hardly applicable to the GHz frequency region. On the otherhand, the anisotropy magnetic field required for actualizing theresonance frequency of 2 GHz is 36 Oe (2864.88 A/m) for the saturationmagnetization of 14 kG (1.4 T) and 28 Oe (2228.24 A/m) for thesaturation magnetization of 18 kG (1.8 T); thus it can be expected thatincorporation of an Fe-based alloy or an FeCo-based alloy, both high insaturation magnetization and magnetic crystalline anisotropy, realizesthe required saturation magnetization and anisotropy magnetic field.

Alloys comprising as the main component Fe or FeCo have hitherto beenwidely known as materials exhibiting high saturation magnetization.However, when the magnetic thin film of an Fe-based alloy or anFeCo-based alloy is formed by means of a deposition technique such asthe sputtering technique, the saturation magnetization of the filmobtained is high, but the coercivity thereof is high and the resistivitythereof is low, so that satisfactory high frequency properties thereofcan be hardly obtained. As the main reason for this, the following hasbeen conceived. As shown in FIG. 2, the thin film 101 of the Fe-basedalloy or the FeCo-based alloy, deposited by sputtering or the like,there occurs columnar growth along the direction perpendicular to asubstrate 100, and the generation of the perpendicular magneticanisotropy ascribable to the columnar structure becomes a problem.

However, as a result of the diligent study carried out by the presentinventors, the following findings have been obtained on the Fe—C thinfilm in which Fe is added with a predetermined amount of C (carbon).

(1) An Fe—C thin film having a predetermined thickness has columnarstructure, but when the thickness is of the order of 70 nm or less,excellent soft magnetic properties can be obtained because the aspectratio of the columnar structure (the ratio of the column length to thecolumn width, the length/the width) is small. More specifically, theaverage width of the grown Fe—C columns is about 50 nm, and thedegradation of the soft magnetic properties due to the columnarstructure can be suppressed as far as the thickness is of the order of70 nm for which the aspect ratio of the columnar structure is 1.4 orless. For the purpose of obtaining an Fe—C thin film having such anaspect ratio, as shown in FIG. 3, it is effective that a Co-basedamorphous alloy thin film 111 is interposed between an Fe—C thin film112 and another Fe—C thin film 112. In this way, the continuous columnargrowth of the Fe—C grains can be prevented.

(2) Elaborate examination of the growth process of the Fe—C thin filmhas revealed that a microcrystalline state of 3 nm or less in grain sizeis found in the early stage of the film growth with the film thicknessof the order of 3 nm or less, and the unstable surface ratio isincreased, so that the features of an amorphous substance are exhibited.More specifically, as shown in FIG. 4, the Fe—C thin film 121 isconstituted with an amorphous structure portion 121 a formed on thesubstrate 120 and a columnar structure portion 121 b formed on theamorphous structure portion 121 a. Being amorphous can be judged for thecase of the Fe—C thin film, on the basis of the X-ray diffraction, fromthe absence of the diffraction peak ascribable to the Fe—C bcc (110)crystal plane. A thin film having such amorphous structure, needless tosay, does not turn into columnar structure, and can yield highresistance (100 μΩcm or more) properties attributable to amorphousstructure. Accordingly, adoption of a form in which the film concernedis laminated with a Co-based amorphous alloy thin film can actualize thesoft magnetic properties, needless to say, and high resistance, so thata magnetic thin film high in permeability in the GHz frequency region,suppressed in eddy current loss and high in quality factor can beobtained.

(3) The above described matters (1) and (2) are effective not only forthe Fe—C thin film but also for the FeCo—C thin film, and moreover, evenfor the case where C is replaced with B or N.

In other words, as described above, the present invention has made itpossible to provide a high frequency composite magnetic thin film whichcan easily attain the properties, in the GHz region (1 GHz), such as thereal part (μ′) of the permeability of 200 or more, the quality factor Q(Q=μ′/μ″) of 1 or more and the saturation magnetization of 12 kG (1.2 T)or more, by laminating a Co-based amorphous alloy thin film excellent insoft magnetic properties and an Fe—(C, B, N) thin film or an FeCo—(C, N,B) thin film, both having high saturation magnetization and highmagnetic anisotropy field.

Accordingly, the present invention provides a high frequency magneticthin film, characterized in that the thin film comprises a first layermade of a T-L composition (here, T is Fe or FeCo, L is one or more of C,B and N) and a second layer made of a Co-based amorphous alloy arrangedon either of the surfaces of the first layer.

It is preferable that the high frequency magnetic thin film of thepresent invention is constituted with a multilayer film structure inwhich a plurality of the first layers and a plurality of the secondlayers are laminated, more preferably they are alternately laminated.

It should be noted that these properties can be obtained for the thinfilm as deposited. In other words, the time elapsed from completion ofdeposition is not concerned, but on the basis of the values measuredafter deposition without being subjected to, for example, heat treatmentand the like, the judgment as to whether the properties specified by thepresent invention are provided or not can be made. Incidentally, even inthe case where heat treatment and the like are applied after deposition,those thin films which are provided with the properties specified by thepresent invention are, needless to say, included within the scope of thepresent invention. The same is applicable to what follows.

The properties concerned can be obtained by regulating the thickness ofthe first and second layers. Specifically, in the case where thethickness of the first layer is denoted by T1 and the thickness of thesecond layer is denoted by T2, the above described properties can beobtained by making T1 fall within the range from 3 to 70 nm, and bymaking T1/T2 fall within the range from 0.15 to 3.50.

The properties concerned can be obtained by regulating the thickness ofthe first and second layers. Specifically, in the case where thethickness of the first layer is denoted by T1 and the thickness of thesecond layer is denoted by T2, the above described properties can beobtained by making T1 fall within the range from 0.5 to 3.0 nm, and bymaking T1/T2 fall within the range from 0.8 to 3.0.

Additionally, as a preferable mode of the present invention, theCo-based amorphous alloy constituting the second layer is formed in sucha way that the alloy is mainly composed of Co, and contains at least oneadditional element selected from the group consisting of B, C, Si, Ti,V, Cr, Mn, Fe, Ni, Y, Zr, Nb, Mo, Hf, Ta and W.

Additionally, as another preferable mode of the present invention, theCo-based amorphous alloy is constituted in such a way that the alloy isselected from the group consisting of CoZr, CoHf, CoNb, CoMo, CoZrNb,CoZrTa, CoFeZr, CoFeNb, CoTiNb, CoZrMo, CoFeB, CoZrNbMo, CoZrMoNi,CoFeZrB, CoFeSiB, and CoZrCrMo.

Additionally, as another preferable mode of the present invention, thefirst layer is constituted in such a way that the concentration of theelement L contained therein is 2 to 20 at %.

According to the present invention described above, there is provided acomposite magnetic thin film in which alternately laminated are thefirst layer mainly composed of Fe or FeCo and having, as a single layerfilm, a saturation magnetization of 16 kG (1.6 T) or more, and thesecond layer mainly composed of Co and having, as a single layer film, apermeability of 1,000 or more (the measurement frequency: 10 MHz), asaturation magnetization of 10 kG (1.0 T) or more and a resistivity of100 μΩcm or more are alternately laminated. It is preferable that thefirst layer is mainly constituted with a columnar structure of 1.4 orless in aspect ratio or is constituted with an amorphous structure.

The high frequency magnetic thin film of the present invention can beused as a constituent element of a magnetic device. The high frequencymagnetic thin film constituting this magnetic device is characterized inthat the thin film is a multilayer film comprising a first layer made ofa T-L composition (here, T=Fe or FeCo, L=one or more of C, B and N) anda second layer made of a Co-based amorphous alloy arranged on either ofthe surfaces of the first layer alternately laminated.

The magnetic device of the present invention can be configured such thatthe element comprises high frequency magnetic thin films arranged toface each other and to sandwich a coil. Additionally, the magneticdevice is a planar magnetic device, and the magnetic device can be madeto be an inductor or a transformer. The application to the inductor usedin a monolithic microwave integrated circuit can be cited as apreferable mode of the present invention.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

FIG. 1 is a cross-sectional view of a high frequency magnetic thin filmof the present invention;

FIG. 2 is a schematic cross-sectional view showing the condition of thegrains in an Fe-based thin film or an FeCo-based thin film;

FIG. 3 is a schematic cross-sectional view showing the condition of thegrains in an Fe—C thin film when an Fe—C thin layer and a Co-basedamorphous alloy thin film are laminated;

FIG. 4 is a partially enlarged cross-sectional view of FIG. 3;

FIG. 5 is a graph showing the X-ray diffraction results of a compositemagnetic thin film in which an Fe—C thin film of 3 nm or less in thethickness T1 and a CoZrNb amorphous alloy thin film are laminated;

FIG. 6 is a plan view showing an example of an inductor to which a highfrequency magnetic thin film of the present invention is applied;

FIG. 7 is a cross-sectional view along the A-A line in FIG. 6;

FIG. 8 is a cross-sectional view showing another example of an inductorto which a high frequency magnetic thin film of the present invention isapplied;

FIG. 9 is a plan view showing another example of an inductor to which ahigh frequency magnetic thin film of the present invention is applied;

FIG. 10 is a cross-sectional view along the A-A line in FIG. 9;

FIG. 11 is a graph showing the magnetization curve of a compositemagnetic thin film prepared in Example 1;

FIG. 12 is a graph showing the high frequency permeability properties ofthe composite magnetic thin film prepared in Example 1;

FIG. 13 is a graph showing the magnetization curve of a compositemagnetic thin film prepared in Example 2;

FIG. 14 is a graph showing the high frequency permeability properties ofthe composite magnetic thin film prepared in Example 2;

FIG. 15 is a graph showing the magnetization curve of a compositemagnetic thin film prepared in Example 3;

FIG. 16 is a graph showing the high frequency permeability properties ofthe composite magnetic thin film prepared in Example 3;

FIG. 17 is a cross-sectional image, obtained by means of a transmissionelectron microscope, of a composite magnetic thin film prepared inExample 5;

FIG. 18 is a graph showing the magnetization curve of a compositemagnetic thin film prepared in Example 10;

FIG. 19 is a graph showing the high frequency permeability properties ofthe composite magnetic thin film prepared in Example 10;

FIG. 20 is a graph showing the magnetization curve of a compositemagnetic thin film prepared in Example 11;

FIG. 21 is a graph showing the high frequency permeability properties ofthe composite magnetic thin film prepared in Example 11;

FIG. 22 is a graph showing the magnetization curve of a compositemagnetic thin film prepared in Example 12;

FIG. 23 is a graph showing the high frequency permeability properties ofthe composite magnetic thin film prepared in Example 12;

FIG. 24 is a diagram showing the magnetic properties and the like of themagnetic thin films prepared in Examples 1 to 9 and Comparative Examples1 to 4;

FIG. 25 is a diagram showing the magnetic properties and the like of themagnetic thin films prepared in Examples 10 to 19 and ComparativeExample 5; and

FIG. 26 is a diagram showing the magnetic properties and the like of themagnetic thin films prepared in Examples 20 to 27.

BEST MODE FOR CARRYING OUT THE INVENTION

Description will be made below on an embodiment of one aspect of thepresent invention.

The high frequency magnetic thin film 1 of the present invention is, asshown in a schematic cross-sectional view of FIG. 1, a compositemagnetic thin film comprising a multilayer film configuration in which aCo-based amorphous alloy layer 3 and a T-L composition layer 7 arealternately laminated. In the embodiment shown in FIG. 1, a multilayerfilm configuration composed of 8 layers in total is shown as an example.

The high frequency magnetic thin film 1 has, as the fundamentalconfiguration thereof, a combination of a T-L composition layer 7 and aCo-based amorphous alloy layer 3 arranged on one surface of the T-Lcomposition layer 7.

The “T” in the T-L composition layer 7 is Fe or FeCo, and “L” is one ormore of C, B and N. The thin film made of an alloy mainly composed of Feor FeCo exhibits high saturation magnetization, but tends to be high incoercivity and low in resistivity. Accordingly, the present inventioncomprises the “L” (one or more of C, B and N) capable of improving thesoft magnetic properties. The T-L composition layer 7 includes twodifferent modes. One of the modes is the one having a columnar structurein which the aspect ratio of the T-L composition layer 7 is 1.4 or less;the actualization of this mode permits yielding a high saturationmagnetization and excellent soft magnetic properties. The other mode isan amorphous structure; the actualization of the amorphous structure ofthe T-L composition layer 7 permits attaining a further improvement ofthe soft magnetic properties and a high electric resistance. For thepurpose of achieving some effects in the high frequency properties, itis preferable that the T-L composition layer 7 has, as a single layerfilm, properties such that the saturation magnetization thereof is 1.6 Tor more. Even in the mode having a columnar structure in which theaspect ratio of the T-L composition layer 7 is 1.4 or less, theamorphous structure is formed at the early stage of the thin filmformation, and accordingly the columnar structure in the presentinvention should be interpreted as including this amorphous structureportion.

When the film thickness of the T-L composition layer 7 becomes large andthe aspect ratio thereof exceeds 1.4 to be 2.0 or more, theperpendicular magnetic anisotropy exhibits itself strongly and the softmagnetic properties are deteriorated. In the present invention, it ismost preferable that the aspect ratios of all the grains present in theT-L composition layer 7 are 1.4 or less; however, the present inventionadmits the partial inclusion of the grains of 30% or less, and moreover,10% or less in the aspect ratio increment. Accordingly, in the presentinvention, the thickness (T1) of the T-L composition layer 7 is made tobe 100 nm or less, preferably 70 nm or less. As described above, when T1is 3 nm or less, the T-L composition layer 7 comes to take an amorphousstructure, and no performance degradation of the layer takes place evenwhen T1 is decreased down to, for example, 0.2 nm. However, if T1 is toosmall, the number of the lamination operations is increased, leading toa problem in preparation such that the total deposition time iselongated. Consequently, it is preferable that T1 is 0.5 nm or more, andfurthermore, 1.0 nm or more.

FIG. 5 shows the X-ray diffraction results of a composite magnetic thinfilm in which an Fe—C thin film of 3 nm or less in the thickness T1 anda CoZrNb amorphous alloy thin film are laminated. As shown in FIG. 5,the laminates of 3 nm or less in the thickness of the Fe—C thin filmeach showed diffraction peak of the bcc (110) crystal plane of the Fe—Csystem having a typical broad shape for an amorphous system.

In the T-L composition layer 7 of the present invention, theconcentration of the L element(s) (one or more of C, B and N) containedtherein is 2 to 20 at %, preferably 4 to 10 at %. When the L elementconcentration is less than 2 at %, there tends to occur the columnargrowth of the bcc structure perpendicularly to the substrate, thecoercivity becomes high, and the resistivity comes to be low, making itdifficult to obtain satisfactory high frequency properties. On the otherhand, when the L element concentration exceeds 20 at %, the an isotropicmagnetic filed is decreased and hence the resonance frequency islowered, so that sufficient functioning as a thin film for use in highfrequency applications becomes difficult. Additionally, the adoption ofFeCo as T rather than the adoption of only Fe is preferable because ahigh saturation magnetization can be thereby obtained. In this case, theCo content may be determined within the range of 80 at % or less, andthe content falling within the range from 20 to 50 at % is preferable.The present invention admits the inclusion of other elements within therange giving no adverse effect on the present invention.

The use of the Co-based amorphous alloy in the present invention as thesecond layer is based on the fact that the alloy is high in permeabilityand high in resistance (the resistivity is 100 to 200 μΩcm) and hencethe eddy current loss in the high frequency region can be suppressed.The use of the amorphous alloy also based on the fact that when thesecond layer is made of a crystalline material, the first layer aboveand in contact with the second layer sees the grain growth thereofaffected by the grain structure of the second layer, resulting informing a continuous columnar structure, while when the second layer ismade of an amorphous material, even if the first layer is of thecolumnar structure, the columnar growth is blocked by the second layer,resulting in no continuous columnar structure. It is preferable that theCo-based amorphous alloy layer 3 has the properties, as a single layerfilm, such that a permeability is 1,000 or more (10 MHz), a saturationmagnetization is 10 kG (1.0 T) or more, and a resistivity is 100 μΩcm ormore.

The Co-based amorphous alloy layer 3 as the second layer of the presentinvention is formed in such a way that the alloy layer is mainlycomposed of Co, and contains at least one additional element selectedfrom the group consisting of B, C, Si, Ti, V, Cr, Mn, Fe, Ni, Y, Zr, Nb,Mo, Hf, Ta and W, the alloy layer being mainly constituted with anamorphous phase. The proportion of the additional element(s) (the totalproportion when more than one additional elements are added) is usually5 to 50 at %, preferably 10 to 30 at %. When the proportion of theadditional element(s) is too high, there occurs a problem that thesaturation magnetization comes to be low, while when the proportion ofthe additional element(s) is too low, there occurs a problem that thecontrol of the magnetostriction becomes difficult and no effective softmagnetic properties can be obtained.

Examples of the preferable composition systems for constituting theCo-based amporphous alloy layer 3 include CoZr, CoHf, CoNb, CoMo,CoZrNb, CoZrTa, CoFeZr, CoFeNb, CoTiNb, CoZrMo, CoFeB, CoZrNbMo,CoZrMoNi, CoFeZrB, CoFeSiB, and CoZrCrMo.

By alternately laminating the above described T-L composition layer 7and the above described Co-based amorphous alloy layer 3, there canbeobtained the high frequency magnetic thin film 1 in which the real (μ′)part of the complex permeability at 1 GHz is 400 or more, the qualityfactor Q (Q=μ′/μ″) is 4 or more, and the saturation magnetization is 14kG (1.4 T) or more. Incidentally, in the GHz region (1 GHz), the real(μ′) part of the complex permeability is demanded to take a value ashigh as possible, and no particular upper limit is imposed thereon.Similarly, the saturation magnetization is also demanded to take a valueas high as possible, and no particular upper limit is imposed thereon.

For the purpose of attaining the above described properties, with thethickness of the T-L composition layer 7 denoted by T1 and the thicknessof the Co-based amorphous alloy layer 3 denoted by T2, it is importantthat T1 is made to fall within the range from 3 to 70 nm and T1/T2 ismade to fall within the range from 0.15 to 3.50, preferably from 0.25 to2.50. This is because when this value exceeds 3.50, the aspect ratio ofthe T-L composition layer 7 becomes high, the anisotropy magnetic fieldand the hard axis coercivity (Hch) is sharply increased, and accordinglythe perpendicular magnetic anisotropy appears, so that particularlythere occurs a problem that high quality soft magnetic properties cannotbe obtained. This is also because when this value is less than 0.15, thesaturation magnetization of 14 kG (1.4 T) or more cannot be obtained.

Additionally, by alternately laminating the above described T-Lcomposition layer 7 and the above described Co-based amorphous alloylayer 3, there can be obtained a high frequency magnetic thin film 1 inwhich the real (μ′) part of the complex permeability at 1 GHz is 500 ormore, the quality factor Q (Q=μ′/μ″) is 10 or more, and the saturationmagnetization is 14 kG (1.4 T) or more.

For the purpose of achieving the above described properties, with thethickness of the T-L composition layer 7 denoted by Ti and the thicknessof the Co-based amorphous alloy layer 3 denoted by T2, T1 has only to bemade to fall within the range from 0.5 to 3.0 nm, and T1/T2 has only tobe made to fall within the range from 0.8 to 3.0.

When T1/T2 exceeds 3.0, the FeC grains grow large, and the resistivityof 130 μΩcm or more cannot be obtained. On the other hand, when thisvalue is smaller than 0.8, the proportion of the T-L composition layer7, being imparted high saturation magnetization, comes to be low, andthe resonance frequency can hardly be shifted to the higher frequencies.Thus, T1/T2 is preferably 1.0 or more and 2.5 or less. By making theabove described T1 and T1/T2 fall respectively within the ranges of thepresent invention, there can be actualize a composite thin film havingextremely excellent properties such that the resistivity is 130 μΩcm ormore, the real (μ′) part of the complex permeability is 500 or more, thequality factor Q (Q=μ′/μ″) is 10 or more, and the saturationmagnetization is 14 kG (1.4 T) or more, all at 1 GHz. Here, it should benoted that theses properties are measured, as described above, under thecondition that deposition has been made but heat treatment and the likeare not applied.

In the high frequency magnetic thin film 1 of the present invention, noparticular constraint is imposed on the total number of the laminatedT-L composition layers 7 and the laminated Co-based amorphous alloylayers 3, these two types of layers being alternately laminated;however, the total number of the laminated layers is usually 5 to 3,000,preferably of the order of 10 to 700. In the high frequency magneticthin film 1, the same type of films (the T-L composition layers 7 or theCo-based amorphous alloy layers 3) are usually formed to be the same infilm thickness. However, as rare cases, even the same type of films arepossibly made to be different in deposition thickness depending on thelamination positions. As an extreme case, for example, there possibly isa specification such that the T-L composition layer 7 near the midwayposition is made to be 20 nm in thickness and each of the upper andbottom T-L composition layers 7 is made to be 5 nm in thickness as thecase may be. In such a case, various numerical derivations may be madeon the basis of the arithmetic mean thickness (Tf). In the abovedescribed example, for example, Tf/Tc (Tc is the arithmetic mean filmthickness of the Co-based amorphous alloy layer 3) may be derived byadopting the arithmetic mean Tf=10 nm. Additionally, the high frequencymagnetic thin film 1 of the present invention admits the arrangement ofthe layers other than the Co-based amorphous alloy layer 3 and the T-Lcomposition layer 7.

The thickness of such a high frequency magnetic thin film 1 of thepresent invention is 100 to 2,000 nm, preferably 300 to 1,000 nm. Whenthis value is less than 100 nm, in the case where the thin film isapplied to a planar magnetic device, there possibly occurs a problemthat a desired power can be hardly handled; additionally, as modes ofcore coils provided with the magnetic thin films, to be described laterand shown in FIGS. 9 and 10, there is found a tendency such that theinductance increments as compared to the air core coils are less than10%, causing a problem that the effect of the magnetic thin film cannotbe sufficiently exhibited. On the other hand, when this value exceeds2,000 nm, the high frequency loss due to the skin effect sharply becomeshigh, causing a problem that the loss in the GHz band is increased.

It is preferable that the high frequency magnetic film 1 of the presentinvention is formed by means of a vacuum thin film formation technique,in particular, the sputtering technique. More specifically, there areused the RF sputtering, DC sputtering, magnetron sputtering, ion beamsputtering, inductively coupled RF plasma assisted sputtering, ECRsputtering, faced-targets sputtering, and the like.

As the target for forming the Co-based amorphous alloy layer 3, acomposite target may be used in which a pellet of a desired additionalelement is arranged on a Co target, and a target of a Co alloycontaining a desired additional component may be used.

As the target for forming the T-L composition layer 7, a compositetarget may be used in which a pellet of an element L is arranged on anFe (or an Fe—Co alloy) target, or a target of an alloy composed of Fe(or FeCo) and the element L may be used. The concentration regulationfor the element L may be made, for example, by regulating the amount ofthe pellet of the element L.

Incidentally, sputtering is merely one possible mode of the presentinvention, and hence, needless to say, other thin film formationtechniques can be applied. The examples to be described later can bereferred to for the specific deposition methods applied to the highfrequency magnetic thin film 1 of the present invention.

Examples of the substrate 2 (FIG. 1) on which the high frequencymagnetic thin film 1 of the present invention is formed include glasssubstrate, ceramic material substrate, semiconductor substrate, resinsubstrate and the like. Examples of ceramic materials include alumina,zirconia, silicon carbide, silicon nitride, aluminum nitride, steatite,mullite, cordierite, forsterite, spinel and ferrite. It is preferablethat, among these materials, aluminum nitride is used which is high bothin thermal conductivity and in bending strength.

Additionally, the high frequency magnetic thin film 1 of the presentinvention has, as described above, extremely excellent high frequencyproperties and exhibit the performance thereof as deposited at roomtemperature, and accordingly, the thin magnetic film is a material mostsuitable for high frequency integrated circuits such as MMICs preparedby means of the semiconductor processes. Thus, examples of a substrate11, a substrate 21 and a substrate 31 (shown in FIGS. 7, 8 and 10 to bedescribed later) include semiconductor substrates such as Si, GaAs, InPand SiGe substrates.

An example of a planar magnetic device applied to an inductor is shownin FIGS. 6 and 7. FIG. 6 schematically shows a plan view of theinductor, and FIG. 7 schematically shows a cross-section along the A-Aline in FIG. 6.

The inductor 10 shown in these figures comprises the substrate 11,planar coils 12, 12 formed in spiral shape on both surfaces of thesubstrate 11, insulating films 13, 13 formed so as to cover these planarcoils 12, 12 and the substrate 11, and a pair of the high frequencymagnetic thin films 1 of the present invention formed so as to cover therespective insulating films 13, 13. Additionally, the two abovedescribed planar coils 12, 12 are electrically connected to each otherthrough the intermediary of a through hole 15 formed in an approximatelycentral location on the substrate 11. Furthermore, from the planar coils12, 12 on both surface of the substrate 11, terminals 16 for connectionare extended so as to be accessible from the outside. Such an inductor10 is constituted in such a way that a pair of the high frequencymagnetic thin films 1 sandwich the planar coils 12, 12 through theintermediary of the insulating films 13, 13, so that an inductor isformed between the connection terminals 16, 16.

The inductor formed in this way is small and thin in shape and light inweight, and exhibits excellent inductance particularly in the highfrequency band of 1 GHz or above.

Additionally, in the above described inductor 10, a transformer can beformed by arranging a plurality sets of the planar coils 12, 12 in aparallel manner.

FIG. 8 shows another preferred embodiment in which the planar magneticdevice of the present invention is applied to an inductor. FIG. 8schematically shows a cross-sectional view of the inductor. As shown inthis figure, an inductor 20 comprises a substrate 21, an oxide film 22formed according to need on the substrate 21, a high frequency magneticthin film 1 a of the present invention formed on the oxide film 22, andan insulating film 23 formed on the high frequency magnetic thin film 1a, and furthermore, has planar coils 24 formed on the insulating film23, an insulating film 25 formed so as to cover these planar coils 24and the insulating film 23, and a high frequency magnetic thin film 1 bof the present invention formed on the insulating film 25. The inductor20 formed in this way is also small and thin in shape and light inweight, and exhibits excellent inductance particularly in the highfrequency band of 1 GHz or above. Additionally, in the inductor 20 asdescribed above, a transformer can be formed by arranging a plurality ofthe planar coils 24 in a parallel manner.

In this connection, the planar magnetic devices such as the thin filminductors are demanded to provide the optimal permeability according tothe design specifications for respective elements. The permeability inthe high frequency band is highly correlated with the anisotropymagnetic field, and is proportional to the reciprocal of the anisotropymagnetic field. For the purpose of actualizing high permeability in thehigh frequency region, it is necessary that there is found the uniaxialanisotropy in the plane of the magnetic thin film. In the planarmagnetic devices such as the thin film inductors, it can be expectedthat the higher is the saturation magnetization of a magnetic thin film,the higher is the DC superposition properties. Consequently, themagnitude of the saturation magnetization can be said to be an importantparameter in the design of the high frequency magnetic thin film 1.

FIGS. 9 and 10 show an example in which the high frequency magnetic thinfilm 1 of the present invention is applied as an inductor for use in anMMIC.

FIG. 9 is a schematic plan view showing the conductive layer portionextracted from the inductor, and FIG. 10 is a schematic sectional viewalong the A-A in FIG. 9.

An inductor 30 illustrated by these figures comprises, as FIG. 10 shows,a substrate 31, an insulating oxide film 32 formed according to need onthe substrate 31, a high frequency magnetic thin film 1 a of the presentinvention formed on the insulating oxide film 32, and an insulating film33 formed on the high frequency magnetic thin film 1 a, and furthermore,has a spiral coil 34 formed on the insulating film 33, an insulatingfilm 35 formed so as to cover the spiral coil 34 and the insulating film33, and a high frequency magnetic thin film 1 b of the present inventionformed on the insulating film 35.

Additionally, the spiral coil 34 is connected to a pair of electrodes 37through the intermediary of the transmission lines 36 as shown in FIG.9. A pair of ground patterns 39 arranged so as to surround the spiralcoil 34 are respectively connected to a pair of ground electrodes 38,thus forming a shape in which the frequency properties are evaluated ona wafer by means of a ground-signal-ground (G-S-G) probe.

The inductor for use in an MMIC involving the shape of the presentembodiment adopts a core structure in which the spiral coil 34 issandwiched by the high frequency magnetic thin films 1 a, 1 b to formthe core. Consequently, the inductance is improved by about 50% whencompared with an inductor with air core structure in which the spiralcoil 34 has the same shape but the high frequency magnetic thin films 1a, 1 b are not formed. Thus, the occupation area needed for attainingthe same inductance can be made smaller, and consequently theminiaturization of the spiral core 34 can be actualized.

In this connection, the material for the magnetic thin film applied tothe inductors for use in an MMIC is required to have a high permeabilityfor the high frequencies and high quality factor Q (low loss) propertiesin the GHz band and to permit the integration in the semiconductorfabrication process.

For the purpose of actualizing the high permeability for the highfrequencies in the GHz band, materials high both in resonance frequencyand saturation magnetization are advantageous, and the control of theuniaxial magnetic anisotropy is necessary. Additionally, for the purposeof attaining a high quality factor Q, the suppression of the eddycurrent loss caused by high resistance is important. Furthermore, forthe purpose of application to the integration process, it is desirablethat deposition can be performed at room temperature, and the films thusformed can be used as deposited. This is because the performances of theother on-chip components that have already undergone setting are madeand the fabrication process to be free from the possible adverse effectscaused by heating.

Now, further detailed description will be made below on the presentinvention with reference to specific examples.

EXAMPLE 1

According to the following deposition technique, a high frequencymagnetic thin film of the present invention was prepared.

An Si wafer on which a 100 nm thick SiO₂ was deposited was used as thesubstrate.

The high frequency magnetic thin film was deposited on the substrate byuse of a faced-targets sputtering apparatus and according to thefollowing techniques. Preliminary evacuation of the interior of thefaced-targets sputtering apparatus was carried out to 8×10⁻⁵ Pa,thereafter Ar gas was introduced into the apparatus until the pressurereached 10 Pa, and then the substrate surface was subjected to sputteretching at an RF power of 100 W for 10 minutes.

Subsequently, the Ar gas flow rate was adjusted so as for the pressureto be 0.4 Pa, at a power of 300 W, a Co₈₇Zr₅Nb₈ target and a compositetarget composed of an Fe target and C (carbon) pellets arranged thereonwere alternately and repeatedly subjected to sputtering, and thus acomposite magnetic thin film was deposited as the high frequencymagnetic thin film formed according to the specifications to bedescribed later.

At the time of deposition, a DC bias of −40 to −80 V was applied to thesubstrate. For the purpose of preventing the effects of impurities onthe surfaces of the targets, the sputtering was conducted for 10 minutesor more with a shutter in a closed condition. Thereafter, with theshutter opened, the deposition onto the substrate was carried out. Thedeposition rates were 0.33 nm/sec for the CoZrNb layer deposition and0.27 nm/sec for the Fe—C layer deposition. By controlling the openingand closing times of the shutter, the film thickness of the respectivelayers, being alternately laminated, were regulated. After a CoZrNblayer was deposited as the first layer on the substrate, a Fe—C layerwas formed thereon, and then successively the CoZrNb layer and the Fe—Clayer were laminated in an alternate manner.

On the basis of the deposition method described above, the 20 nm thickCoZrNb layer and the 5 nm thick Fe—C layer (carbon concentration: 5 at%) were alternately laminated 20 times for each layer in a successivemanner, and thus a composite magnetic thin film (Example 1) of thepresent invention, having a total film thickness of 500 nm (40 layers intotal) was formed.

Examination of the structure of the composite magnetic thin filmconfirmed that the Fe—C layers were composed of the above describedamorphous structure portion and the columnar structure portion formedthereon, and the aspect ratio of the columnar structure portion was 1.4or less. Additionally, the CoZrNb layers were confirmed to be amorphous.

FIG. 11 shows the magnetization curve measured after deposition. As isclear from the magnetization curve shown in FIG. 11, the in-planeuniaxial magnetic anisotropy was observed in the laminated film, and avalue of 14.7 kG (1.47 T) was obtained for the saturation magnetization,a value of 45 Oe (3580.99 A/M) was obtained for the anisotropy field,and a value of 1.1 Oe (87.53 A/m) was obtained for the easy axiscoercivity.

Additionally, FIG. 12 shows the high frequency permeability propertiesof the composite magnetic thin film. As shown in the graph of FIG. 12,the resonance frequency exceeds the measurement limit of 2 GHz, and thereal part (μ′) of the permeability in the GHz region is 400 or more.Additionally, for the quality factor Q (Q=μ′/μ″), a value of 13 wasobtained at 1 GHz and a value of 2 or more was obtained at 2 GHz. Thehigh frequency permeability measurement was made by use of a thin filmhigh frequency permeability measurement apparatus (Naruse KagakukikiCo., RHF-F1000), and the magnetic properties were measured by use of avibrating sample magnetometer (Riken Denshi Co., Ltd., BHV-35).

EXAMPLE 2

On the basis of the above described deposition technique of Example 1, a20 nm thick CoZrNb layer and a 20 nm Fe—C layer (carbon concentration: 5at %) were alternately laminated each in 13 layers in a successivemanner, and thus a composite magnetic thin film (Example 2) of thepresent invention having a total film thickness of 520 nm (26 layers intotal) was formed.

Examination of the structure of the composite magnetic thin filmconfirmed that the Fe—C layers were mainly constituted with columnargrains and the aspect ratio of the columnar structure portion was 1.4 orless. Additionally, the CoZrNb layers were confirmed to be amorphous.

FIG. 13 shows the magnetization curve measured after deposition. As isclear from the magnetization curve shown in FIG. 13, the in-planeuniaxial magnetic anisotropy was observed in the laminated film, and avalue of 16.3 kG (1.63 T) was obtained for the saturation magnetization,a value of 44 Oe (3501.41 A/m) was obtained for the anisotropy field,and a value of 1.2 Oe (95.49 A/m) was obtained for the easy axiscoercivity.

Additionally, FIG. 14 shows the high frequency permeability propertiesof the composite magnetic thin film. As shown in the graph of FIG. 14,for the real part (μ′) of the permeability, a value of 540 was obtainedat 1 GHz and a value of 670 was obtained at 1.5 GHz. Additionally, forthe quality factor Q (Q=μ′/μ″), a value of 4.7 was obtained at 1 GHz anda value of 2 or more was obtained at 1.5 GHz.

EXAMPLE 3

On the basis of the above described deposition technique of Example 1, a20 nm thick CoZrNb layer and a 50 nm Fe—C layer (carbon concentration: 5at %) were alternately laminated each in 7 layers in a successivemanner, and thus a composite magnetic thin film (Example 3) of thepresent invention having a total film thickness of 490 nm (14 layers intotal) was formed.

Examination of the structure of the composite magnetic thin filmconfirmed that the Fe—C layers were mainly constituted with columnargrains and the aspect ratio of the columnar structure portion was 1.4 orless. Additionally, the CoZrNb layers were confirmed to be amorphous.

FIG. 15 shows the magnetization curve measured after deposition. As isclear from the magnetization curve shown in FIG. 15, the in-planeuniaxial magnetic anisotropy was observed in the laminated film, and avalue of 16.7 kG (1.67 T) was obtained for the saturation magnetization,a value of 48 Oe (3819.72 A/m) was obtained for the anisotropy field,and a value of 1.60 Oe (127.32 A/m) was obtained for the easy axiscoercivity.

Additionally, FIG. 16 shows the high frequency permeability propertiesof the composite magnetic thin film. As shown in the graph of FIG. 16,the real part (μ′) of the permeability is 500 or more in the GHz region.Additionally, for the quality factor Q (Q=μ′/μ″), a value of 6 or morewas obtained at 1 GHz and a value of 2 or more was obtained at 2 GHz.

EXAMPLE 4

On the basis of the above described deposition technique of Example 1, a20 nm thick CoZrNb layer and a 2 nm Fe—C layer (carbon concentration: 5at %) were alternately laminated each in 20 layers in a successivemanner, and thus a composite magnetic thin film (Example 4) of thepresent invention having a total film thickness of 440 nm (40 layers intotal) was formed.

Examination of the structure of the composite magnetic thin filmconfirmed that the Fe—C layers and the CoZrNb layers were bothamorphous.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm were measured, and thus a saturation magnetization of 12.5 kG (1.25T), an anisotropy field of 20 Oe (1591.55 A/m), and an easy axiscoercivity of 1.10 Oe (87.53 A/m) were obtained.

Additionally, a value of 900 for the real part (μ′) of the permeabilityat 1 GHz and a value of 1.3 for the quality factor Q (Q=μ′/μ″) at 1 GHzwere obtained.

EXAMPLE 5

On the basis of the above described deposition technique of Example 1, a20 nm thick CoZrNb layer and a 80 nm Fe—C layer (carbon concentration: 5at %) were alternately laminated each in 7 layers in a successivemanner, and thus a composite magnetic thin film (Example 5) of thepresent invention having a total film thickness of 700 nm (14 layers intotal) was formed.

FIG. 17 shows a sectional view of the composite magnetic thin film,obtained by means of a transmission electron microscope; it wasconfirmed that the Fe—C layers were mainly constituted with columnargrains and the aspect ratio of the columnar structure portion was 1.4 orless.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of18.0 kG (1.80 T), an anisotropy field of 92 Oe (7321.13 A/m), and aneasy axis coercivity of 2.8 Oe (222.82 A/m) were obtained.

Additionally, a value of 200 for the real part (μ′) of the permeabilityat 1 GHz and a value of 8 for the quality factor Q (Q=μ′/μ″) at 1 GHzwere obtained.

EXAMPLE 6

A composite magnetic thin film (Example 6) of the present invention wasformed in the same manner as that in Example 1 except that the carbonconcentration in the Fe—C layer was altered from 5 at % to 7 at %.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of14.7 kG (1.47 T), an anisotropy field of 42 Oe (3342.25 A/m), and aneasy axis coercivity of 1.0 Oe (79.58 A/m) were obtained.

Additionally, a value of 410 for the real part (μ′) of the permeabilityat 1 GHz and a value of 14 for the quality factor Q (Q=μ′/μ″) at 1 GHzwere obtained.

EXAMPLE 7

A composite magnetic thin film (Example 7) of the present invention wasformed in the same manner as that in Example 1 except that the carbonconcentration in the Fe—C layer was altered from 5 at % to 10 at %.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of14.5 kG (1.45 T), an anisotropy field of 40 Oe (3183.10 A/m), and aneasy axis coercivity of 1.0 Oe (79.58 A/m) were obtained.

Additionally, a value of 490 for the real part (μ′) of the permeabilityat 1 GHz and a value of 11 for the quality factor Q (Q=μ′/μ″) at 1 GHzwere obtained.

COMPARATIVE EXAMPLE 1

A composite magnetic thin film (Comparative Example 1) of thecomparative example was formed in the same manner as that in Example 1except that the Fe—C layers was replaced with the Fe layers.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of17.6 kG (1.76 T), an anisotropy field of 28 Oe (2228.24 A/m), and aneasy axis coercivity of 18.0 Oe (1432.44 A/m) were obtained.

Additionally, a value of 120 for the real part (μ′) of the permeabilityat 1 GHz and a value of 4 for the quality factor Q (Q=μ′/μ″) at 1 GHzwere obtained.

EXAMPLE 8

A composite magnetic thin film (Example 8) of the present invention wasformed in the same manner as that in Example 1 except that thecomposition of the Co-based amorphous alloy layer was altered fromCo₈₇Zr₅Nb₈ to Co₈₉Zr₆Ta₅.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of14.9 kG (1.49 T), an anisotropy field of 44 Oe (3501.44 A/m), and aneasy axis coercivity of 1.1 Oe (87.53 A/m) were obtained.

Additionally, a value of 455 for the real part (μ′) of the permeabilityat 1 GHz and a value of 11 for the quality factor Q (Q=μ′/μ″) at 1 GHzwere obtained.

EXAMPLE 9

A composite magnetic thin film (Example 9) of the present invention wasformed in the same manner as that in Example 1 except that thecomposition of the Co-based amorphous alloy layer was altered fromCo₈₇Zr₅Nb₈ to Co₈₀Fe₉Zr₃B₈.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of14.7 kG (1.47 T), an anisotropy field of 48 Oe (3919.72 A/m), and aneasy axis coercivity of 1.2 Oe (95.49 A/m) were obtained.

Additionally, a value of 410 for the real part (μ′) of the permeabilityat 1 GHz and a value of 12 for the quality factor Q (Q=μ′/μ″) at 1 GHzwere obtained.

COMPARATIVE EXAMPLE 2

A composite magnetic thin film (Comparative Example 2) of thecomparative example was formed in the same manner as that in Example 1except that the 500 nm thick composite magnetic thin film was replacedwith a 500 nm thick single layer film made of Co₈₇Zr₅Nb₈.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of11.5 kG (1.15 T), an anisotropy field of 15 Oe (1193.66 A/m), and aneasy axis coercivity of 0.8 Oe (63.66 A/m) were obtained.

Additionally, a value of 1091 for the real part (μ′) of the permeabilityat 1 GHz and a value of 1 for the quality factor Q (Q=μ′/μ″) at 1 GHzwere obtained.

COMPARATIVE EXAMPLE 3

A composite magnetic thin film (Comparative Example 3) of thecomparative example was formed in the same manner as that in Example 1except that the 500 nm thick composite magnetic thin film was replacedwith a 1,000 nm thick single layer film made of Co₈₉Zr₆Ta₅.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of13.0 kG (1.30 T), an anisotropy field of 16 Oe (1273.24 A/m), and aneasy axis coercivity of 0.9 Oe (71.62 A/m) were obtained.

Additionally, a value of 325 for the real part (μ′) of the permeabilityat 1 GHz and a value of 0.5 for the quality factor Q (Q=μ′/μ″) at 1 GHzwere obtained.

COMPARATIVE EXAMPLE 4

A composite magnetic thin film (Comparative Example 4) of thecomparative example was formed in the same manner as that in Example 1except that the 500 nm thick composite magnetic thin film was replacedwith a 1,000 nm thick single layer film made of Co₇₉Fe₉Zr₂Ta₁₀.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of11.0 kG (1.10 T), an anisotropy field of 36 Oe (2864.79 A/m), and aneasy axis coercivity of 1.1 Oe (87.53 A/m) were obtained.

Additionally, a value of 327 for the real part (μ′) of the permeabilityat 1 GHz and a value of 1.7 for the quality factor Q (Q=μ′/μ″) at 1 GHzwere obtained.

FIG. 24 collects the magnetic properties and the like of the magneticthin films prepared in Examples 1 to 9 and Comparative Examples 1 to 4.

As shown in FIG. 24, the respective examples according to the presentinvention can attain a saturation magnetization of 1.2 T or more, aresonance frequency of 1.5 GHz or more, and a Q value of 1.0 or more.Among these examples, Examples 1 to 3, 6, 7, 8 and 9 in which T1 fallswithin the range from 3 to 70 nm and T1/T2 falls within the range from0.15 to 3.50 can attain a saturation magnetization of 1.4 T or more, aresonance frequency of 2.0 GHz or more, and a Q value of 4.0 or more.

EXAMPLE 10

On the basis of the same manner as that in Example 1 except that an Siwafer on which SiO₂ was deposited in a thickness of 500 nm was used asthe substrate, the 1.0 nm thick CoZrNb layer and the 1.0 nm thick Fe—Clayer (carbon concentration: 5 at %) were alternately laminated 250times for each layer in a successive manner, and thus the compositemagnetic thin film (Example 10) of the present invention, having a totalfilm thickness of 500 nm (500 layers in total) was formed. Incidentally,the substrate temperature was not controlled during deposition, and thusthe substrate temperature had been increased to 30° C. by the time whendeposition was made until the total film thickness reached a value of500 nm.

Examination of the structure of the composite magnetic thin filmconfirmed that the Fe—C layers and the CoZrNb layers were bothamorphous.

FIG. 18 shows the magnetization curve measured after deposition. As isclear from the magnetization curve shown in FIG. 18, the in-planeuniaxial magnetic anisotropy was observed in the laminated film, and avalue of 14.3 kG (1.43 T) was obtained for the saturation magnetization,a value of 0.6 Oe (47.75 A/m) was obtained for the easy axis coercivity,and a value of 0.8 Oe (63.66 A/m) was obtained for the hard axiscoercivity. Additionally, FIG. 19 shows the high frequency permeabilityproperties of the laminate film of the present example. As shown in thegraph of FIG. 19, the resonance frequency exceeds the measurement limitof 2 GHz, and the real part (μ′) of the permeability in the GHz regionis 500 or more. Additionally, for the quality factor Q (Q=μ′/μ″), avalue of 15 was obtained at 1 GHz and a value of 7 was obtained at 2GHz.

EXAMPLE 11

On the basis of the above described deposition technique of Example 10,the 1.5 nm thick CoZrNb layer and the 1.5 nm thick Fe—C layer (carbonconcentration: 5 at %) were alternately laminated each in 170 layers ina successive manner, and thus the composite magnetic thin film (Example11) of the present invention, having a total film thickness of 510 nm(340 layers in total) was formed.

Examination of the structure of the composite magnetic thin filmconfirmed that the Fe—C layers and the CoZrNb layers were bothamorphous.

FIG. 20 shows the magnetization curve measured after deposition. As themagnetic properties obtained from the magnetization curve shown in FIG.20, the saturation magnetization was 15.5 kG (1.55 T), the easy axiscoercivity was 0.6 Oe (47.75 A/m), and the hard axis coercivity was 0.8Oe (63.66 A/m). FIG. 21 shows the high frequency permeability propertiesof the laminate film of the present example. As shown in the graph ofFIG. 21, for the real part (μ′) of the permeability, a value of 720 wasobtained at 1 GHz and a value of 1055 was obtained at 1.5 GHz.Additionally, for the quality factor Q (Q=μ′/μ″) a value of 13 wasobtained at 1.0 GHz and a value of 5 was obtained at 1.5 GHz.

EXAMPLE 12

On the basis of the above described deposition technique of Example 10,the 1.0 nm thick CoZrNb layer and the 2.0 nm thick Fe—C layer (carbonconcentration: 5 at %) were alternately laminated each in 170 layers ina successive manner, and thus the composite magnetic thin film (Example12) of the present invention, having a total film thickness of 510 nm(340 layers in total) was formed.

Examination of the structure of the composite magnetic thin filmconfirmed that the Fe—C layers and the CoZrNb layers were bothamorphous.

FIG. 22 shows the magnetization curve measured after deposition. As themagnetic properties obtained from the magnetization curve shown in FIG.22, the saturation magnetization was 14.8 kG (1.48 T), the easy axiscoercivity was 0.7 Oe (55.70 A/m), and the hard axis coercivity was 1.0Oe (79.58 A/m).

FIG. 23 shows the high frequency permeability properties of the laminatefilm of the present example. As shown in the graph of FIG. 23, theresonance frequency exceeds the measurement limit of 2 GHz, and the realpart (μ′) of the permeability is 500 or more in the GHz region.Additionally, for the quality factor Q (Q=μ′/μ″), a value of 8.5 wasobtained at 1.5 GHz and a value of 3 was obtained at 2 GHz.

EXAMPLE 13

On the basis of the above described deposition technique of Example 10,the 1.0 nm thick CoZrNb layer and the 2.8 nm thick Fe—C layer (carbonconcentration: 5 at %) were alternately laminated each in 135 layers ina successive manner, and thus the composite magnetic thin film (Example13) of the present invention, having a total film thickness of 513 nm(270 layers in total) was formed.

Examination of the structure of the composite magnetic thin filmconfirmed that the Fe—C layers and the CoZrNb layers were bothamorphous.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of15.0 kG (1.50 T), an easy axis coercivity of 0.8 Oe (63.66 A/m), and ahard axis coercivity of 0.9 Oe (71.62 A/m) were obtained.

Additionally, a value of 550 was obtained at 1 GHz for the real part(μ′) of the permeability, and a value of 22 was obtained at 1 GHz forthe quality factor Q (Q=μ′/μ″).

EXAMPLE 14

On the basis of the above described deposition technique of Example 1,the 0.8 nm thick CoZrNb layer and the 2.8 nm thick Fe—C layer (carbonconcentration: 5 at %) were alternately laminated each in 140 layers ina successive manner, and thus the composite magnetic thin film (Example14) of the present invention, having a total film thickness of 504 nm(280 layers in total) was formed.

Examination of the structure of the composite magnetic thin filmconfirmed that the Fe—C layers and the CoZrNb layers were bothamorphous.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of15.8 kG (1.58 T), an easy axis coercivity of 0.9 Oe (71.62 A/m), and ahard axis coercivity of 1.1 Oe (87.54 A/m) were obtained.

Additionally, a value of 400 was obtained at 1 GHz for the real part(μ′) of the permeability, and a value of 16 was obtained at 1 GHz forthe quality factor Q (Q=μ′/μ″).

EXAMPLE 15

On the basis of the above described deposition technique of Example 1,the 2.0 nm thick CoZrNb layer and the 1.0 nm thick Fe—C layer (carbonconcentration: 5 at %) were alternately laminated each in 170 layers ina successive manner, and thus the composite magnetic thin film (Example15) of the present invention, having a total film thickness of 510 nm(340 layers in total) was formed.

Examination of the structure of the composite magnetic thin filmconfirmed that the Fe—C layers and the CoZrNb layers were bothamorphous.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of13.9 kG (1.39 T), an easy axis coercivity of 0.6 Oe (47.75 A/m), and ahard axis coercivity of 0.7 Oe (55.70 A/m) were obtained.

Additionally, a value of 755 was obtained at 1 GHz for the real part(μ′) of the permeability, and a value of 6 was obtained at 1 GHz for thequality factor Q (Q=μ′/μ″).

COMPARATIVE EXAMPLE 5

On the basis of the same manner as that in Example 10 except that theFe—C layers were replaced with the Fe layers, the composite magneticthin film (Comparative Example 5) of the comparative example was formed.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of20.7 kG (2.07 T), an easy axis coercivity of 4.2 Oe (334.23 A/m), and ahard axis coercivity of 19.0 Oe (1511.97 A/m) were obtained.

Additionally, a value of 150 was obtained at 1 GHz for the real part(μ′) of the permeability, but the permeability was so low that theobserved value of μ″ was not reliable, and hence the quality factor Q(Q=μ′/μ″) was not able to be obtained.

EXAMPLE 16

On the basis of the same manner as that in Example 10 except that thecarbon concentration of the Fe—C layer was altered from 5 at % to 7 at%, a composite magnetic thin film (Example 16) of the present inventionwas formed.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of14.1 kG (1.41 T), an easy axis coercivity of 0.6 Oe (47.75 A/m), and ahard axis coercivity of 0.7 Oe (55.76 A/m) were obtained.

Additionally, a value of 600 was obtained at 1 GHz for the real part(μ′) of the permeability, and a value of 12 was obtained at 1 GHz forthe quality factor Q (Q=μ′/μ″).

EXAMPLE 17

On the basis of the same manner as that in Example 10 except that thecarbon concentration of the Fe—C layer was altered from 5 at % to 10 at%, a composite magnetic thin film (Example 17) of the present inventionwas formed.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of14.0 kG (1.40 T), an easy axis coercivity of 0.6 Oe (47.75 A/m), and ahard axis coercivity of 0.7 Oe (55.76 A/m) were obtained.

Additionally, a value of 750 was obtained at 1 GHz for the real part(μ′) of the permeability, and a value of 12 was obtained at 1 GHz forthe quality factor Q (Q=μ′/μ″).

EXAMPLE 18

On the basis of the same manner as that in Example 10 except that thecomposition of the Co-based amorphous alloy layer was altered fromCo₈₇Zr₅Nb₈ to Co₈₉Zr₆Ta₅, a composite magnetic thin film (Example 18) ofthe present invention was formed.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of14.4 kG (1.44 T), an easy axis coercivity of 0.6 Oe (47.75 A/m), and ahard axis coercivity of 0.7 Oe (55.76 A/m) were obtained.

Additionally, a value of 520 was obtained at 1 GHz for the real part(μ′) of the permeability, and a value of 15 was obtained at 1 GHz forthe quality factor Q (Q=μ′/μ″).

EXAMPLE 19

On the basis of the same manner as that in Example 10 except that thecomposition of the Co-based amorphous alloy layer was altered fromCo₈₇Zr₅Nb₈ to Co₈₀Fe₉Zr₃B₈, a composite magnetic thin film (Example 19)of the present invention was formed.

On the basis of the methods in conformity with the above describedexamples, the physical property values of the composite magnetic thinfilm concerned were measured, and thus a saturation magnetization of15.0 kG (1.50 T), an easy axis coercivity of 0.6 Oe (47.75 A/m), and ahard axis coercivity of 0.7 Oe (55.76 A/m) were obtained.

Additionally, a value of 530 was obtained at 1 GHz for the real part(μ′) of the permeability, and a value of 17 was obtained at 1 GHz forthe quality factor Q (Q=μ′/μ″).

FIG. 25 collects the magnetic properties and the like of the magneticthin films prepared in Examples 10 to 19 and Comparative Example 5.

As shown in FIG. 25, the respective examples according to the presentinvention can attain a saturation magnetization of 1.4 T or more, aresonance frequency of 1.5 GHz or more, and a Q value of 5.0 or more.Among these examples, Examples 10 to 13, 16, 17, 18 and 19 in which T1falls within the range from 0.5 to 3.0 nm and T1/T2 falls within therange from 0.8 to 3.0 can attain a saturation magnetization of 1.4 T ormore, a resonance frequency of 2.0 GHz or more, and a Q value of 10.0 ormore.

EXAMPLES 20 TO 27

On the basis of the same manner as that in Example 1 except that thetargets for use in thin film formation were the targets described below,the magnetic thin films shown in FIG. 26 were formed, and the physicalproperties thereof such as the magnetic properties and the like weremeasured. The results obtained are collected in FIG. 26.

For the magnetic thin films containing the Fe—Co—C₅ film, a compositetarget wherein C (carbon) pellets were arranged on an Fe₇₀Co₃₀ targetwas used. For the magnetic thin films containing the Fe—B₅ film, anFe₉₅B₅ alloy target was used, and for the magnetic thin films containingthe Fe—Co—B₅ film, a Fe₆₅Co₃₀B₅ alloy target was used. The magnetic thinfilms containing the Fe—C₅—N₅ film were prepared by introducing N(nitrogen) gas during sputtering using a composite target wherein Cpellets were arranged on an Fe target, and the magnetic thin filmscontaining the FeCo—C₅—N₅ film were prepared by introducing N (nitrogen)gas during sputtering using a composite target wherein C pellets werearranged on an Fe₇₀Co₃₀ target.

As shown by Example 20 in FIG. 26, by adopting the Fe—Co—C₅ film as thefirst film, as compared to Example 1 in which the Fe—C₅ film was adoptedas the first film, the saturation magnetization and the real part of thepermeability were improved.

Additionally, from Examples 21 to 25 in FIG. 26, it can be seen that forthe first film, not only C but also B and/or N can be applied.

Yet additionally, from a comparison between Examples 20, 26 and 27 inFIG. 26, it can be seen that for the purpose of attaining particularlyexcellent properties, it is important to regulate both T1 and T1/T2.

INDUSTRIAL APPLICABILITY

As described above in detail, according to the present invention, a highfrequency magnetic thin film which has a high saturation magnetization,and concurrently exhibits a high permeability and a high quality factorQ in the high frequency of GHz range can be provided.

1. A high frequency magnetic thin film comprising: a first layercomprising a T-L composition (here, T is Fe or FeCo, L is B); and asecond layer comprising a Co-based amorphous alloy arranged on either ofthe surfaces of said first layer wherein: said first layer has a bccstructure.
 2. A high frequency magnetic thin film according to claim 1,wherein: a plurality of said first layers and one or more said secondlayers are laminated to form a multilayer film structure.
 3. A highfrequency magnetic thin film according to claim 1, wherein: the realpart (μ′) of the complex permeability at 1 GHz is 400 or more, thequality factor Q (μ′/μ″) is 4 or more, and the saturation magnetizationis 14 kG (1.4 T) or more.
 4. A high frequency magnetic thin filmaccording to claim 1, wherein: when T1 denotes the thickness of saidfirst layer and T2 denotes the thickness of said second layer, T1 fallswithin the range from 3 to 70 nm and T1/T2 falls within the range from0.15 to 3.50.
 5. A high frequency magnetic thin film according to claim1, wherein: the real part (μ′) of the complex permeability at 1 GHz is500 or more, the quality factor Q (μ′/μ″) is 10 or more, and thesaturation magnetization is 14 kG (1.4 T) or more.
 6. A high frequencymagnetic thin film according to claim 5, wherein: when T1 denotes thethickness of said first layer and T2 denotes the thickness of saidsecond layer, the thickness of said first layer T1 falls within therange from 0.5 to 3.0 nm and T1/T2 falls within the range from 0.8 to3.0.
 7. A high frequency magnetic thin film according to 1, wherein:said second layer is mainly composed of Co, and comprises at least oneadditional element selected from the group consisting of B, C, Si, Ti,V, Cr, Mn, Fe, Ni, Y, Zr, Nb, Mo, Hf, Ta and W.
 8. A high frequencymagnetic thin film according to 1, wherein: said second layer isselected from the group consisting of CoZr, CoHf, CoNb, CoMo, CoZrNb,CoZrTa, CoFeZr, CoFeNb, CoTiNb, CoZrMo, CoFeB, CoZrNbMo, CoZrMoNi,CoFeZrB, CoFeSiB and CoZrCrMo.
 9. A high frequency magnetic thin filmaccording to claim 1, wherein: the concentration of the element Lcontained in said first layer falls within the range from 2 to 20 at %.10. A high frequency magnetic thin film according to claim 1, wherein: aplurality of said first layers and a plurality of said second layers arelaminated to form a multilayer film structure.
 11. A high frequencymagnetic thin film according to claim 1, wherein: said L furthercomprises C.
 12. A composite magnetic thin film, comprising: a firstlayer which is mainly composed of Fe or FeCo and B, with the saturationmagnetization of 16 kG (1.6 T) or more by itself, and said first layeris constituted with a columnar structure of 1.4 or less aspect ratio oran amorphous structure, and a second layer which is mainly composed ofCo, having the properties by itself that the permeability is 1,000 ormore (the measurement frequency: 10 MHz), the saturation magnetizationis 10 kG (1.0 T) or more, and the resistivity is 100 μΩ cm or more,wherein: said first layer and said second layer are alternatelylaminated and said first layer has a bcc structure.
 13. A magneticdevice comprising a high frequency magnetic thin film, wherein: saidhigh frequency magnetic thin film is a multilayer film wherein a firstlayer comprising a T-L composition (here, T is Fe or FeCo, L is B) and asecond layer comprising a Co-based amorphous alloy arranged on either ofthe surfaces of said first layer are alternately laminated, wherein:said first layer has a bcc structure.
 14. A magnetic device according toclaim 13, wherein: said magnetic device comprises said high frequencymagnetic thin films arranged to face each other so as to sandwich acoil.
 15. A magnetic device according to claim 14, wherein: saidmagnetic device is an inductor or a transformer.
 16. A magnetic deviceaccording to claim 14, wherein: said magnetic device is an inductor usedin a monolithic microwave integrated circuit.
 17. A magnetic deviceaccording to claim 13, wherein: said L further comprises C.